Steamboy HSMT-400 Water Heated Mattress Topper Unlike other heated mattress toppers that use electric which emits electromagnetic waves that can be harmful to your body, the Steamboys heated mattress toppers use water circulation technology. It provides a safe and relaxing sleep as as heated water circulates throughout the topper while other heating pads such as electric heating pads have the risk of fire and emit dangerous electromagnetic waves. Steamboys cutting edge technology heats the water and then circulates the warm water throughout the mattress topper to provide warmth and a good nights rest. Low power consumption design boasts high efficiency and low energy cost (You save 10% off your heating bill by lowering your thermostat 5 degrees lower) Number one brand in Korea with 60% of the market